The advent of antiretroviral therapy (ART) has drastically changed the epidemiology of Acquired Immunodeficiency Syndrome (AIDS). Indeed, human immunodeficiency virus (HIV) patients treated with ART can expect to live for decades and chronic diseases, such as atherothrombosis, are replacing acute infections as important causes of morbidity and death. In the current proposal we unexpectedly demonstrate that megakaryocytes and platelets express endogenous reverse transcriptase (RT) activity, which is specifically blocked by nucleoside analog RT inhibitors (NRTIs) and non-nucleoside RT inhibitors (NNRTIs). We also show that inhibition of platelet RT activity leads to the loss of translational repression and the formation of stress platelets, which are hyperactive and prone to cause thrombosis. Our robust preliminary data will be leveraged to test the overall hypothesis that ART induces platelet malfunction by directly inhibiting endogenous RT activity in megakaryocytes and platelets, which contributes to the development of atherothrombosis in HIV patients. These aims will be executed by a research team with expertise in platelet biology, virology, thrombosis, and HIV that includes two early stage investigators with outstanding track records. Moreover, this team includes both basic scientists and clinician scientists, providing a strong, multidisciplinary group of investigators that has the experience and training to successfully complete these investigations. Questions proposed by our multi-investigator team are innovative because they explore a novel activity of megakaryocytes and platelets, reverse transcriptase, that may have previously-unrecognized functional consequences in health and disease. They also have immediate clinical significance because new information will be generated regarding the off-target effects of ART that contribute to HIV-related atherothrombosis. Dissecting the mechanisms by which ART regulates reverse transcriptase activity in megakaryocytes and platelets will shed light on how this molecular pathway operates and functions in eukaryotic cells and, in parallel, provide insight into how ART contributes to atherothrombotic events in patients with HIV.